Electron tube with resonator tuning by deformation of an internal tubular member



G. M. W. BADGER ITH RESONATOR TUNING BY DEFORMATI Feb. 21, 1967 3,305,802

ELEcTRoN TUBE w ON OF AN INTERNAL TUBULAR MEMBER Filed May 27, 1963 ATTORNEY United States Patent M 3,305,802 ELECTRON TUBE WITH RESONATOR TUNING BY DEFORMATION OF AN INTERNAL TUBULAR MEMBER George M. W. Badger, Menlo Park, Calif., assignor, by mesne assignments, to Varian Associates, a corporation of California Filed May 27, 1963, Ser. No. 283,210 Claims. (Cl. 333-83) This invention relates generally to electron tubes and more particularly to a simplified tuner for cavities used in conjunction therewith.

In many classes of high frequency electron tubes, the resonant cavity walls form a portion of the envelope. In certain types of these tubes, the cavity must be capable of being tuned over a relatively wide range of frequencies so that the tube can be adjusted to operate at various frequencies. In this type tube, relatively complicated and expensive vacuum seals are required to permit movement of a tuning member maintaining a sealed envelope. Other tubes are operated at fixed frequencies and the cavity is tuned during manufacture or after installation. The cavity then remains in its fixed tuned position. For this purpose, it has been sufficient to distort the cavity moderately as by distorting the walls of the cavity. However, this requires a skilled technician or engineer in order to provide the requisite distortion of the cavity.

Of course, fixed tuned cavities might be provided with tuners which extend into the cavity in sealed relationship therewith. However, such tuners would again be relatively expensive because of the necessity of providing a tight envelope for the electron tube.

It is, therefore, a general object of the invention to provide an improved means for tuning electron tubes of the cavity type.

It is a more particular object of this invention to provide a simplified tuner for resonant cavities.

It is still another object of this invention to provide vide a tuner for fixed tuned resonant cavities of the aforementioned character which is relatively inexpensive to manufacture and simple to employ.

It is still a further object of the present invention to provide a tuner of the aforementioned character which, after initial tuning, is relatively insensitive to handling of the resonant cavity or the vacuum tube itself.

These and other features of the invention will become more clearly apparent upon review of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a view partially in elevation and partially in cross-section of an electron tube of the klystron type employing an integral resonant cavity in accordance with one embodiment of this invention;

FIGURE 2 is an enlarged perspective view of a resonant cavity, such as the ones shown in FIGURE 1;

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 1 with an adjusting tool inserted within the tuner;

FIGURE 4 is a sectional view taken along the line 44 of FIGURE 3;

FIGURE 5 is a sectional view taken along the axis of a cavity similar to that shown in FIGURE 2 but showing another embodiment of the tuner;

FIGURE 6 is a sectional view taken along the line 6-6 of FIGURE 5; and

FIGURE 7 is a sectional view showing a tuner used with an external resonant cavity.

Referring to FIGURE 1, one type of electron tube to which the invention is applicable is illustrated and is a klystron tube including a gun 13, a plurality of resonant 3,305,802 Patented Feb. 21, 1967 cavities 15, 17 and 19 connected by drift tube sections 21, 23 and 25 and a collector electrode 27. The drift tube sections 21, 23 and 25 are separated by interaction gaps 29, 31 and 33 within each of the cavities 15, 17 and 19.

The gun produces a beam of electrons which is directed axially through the drift tube sections towards the collector electrode. Electron flow is accomplished by maintaining the drift tube sections and the collector electrode at a positive electrical potential with respect to the cathode of the gun 13.

The input cavity 15 may be excited by means of, for example, a loop coupler 35 to produce electromagnetic fields in the cavity which give rise to voltage variations which appear across the interaction gap 29. The velocity of the electrons crossing this gap will be modulated by the voltage fields at the gap, as is well known in the klystron art. The velocity modulation of the electron beam causes 'bunching of the electrons. The bunched electrons, in passing the interaction gap 31 at the cavity 17, excite this cavity which, in turn, produces electric fields at the gap which provide additional velocity modulation to further bunch the electrons in the beam.

As the bunched electron beam crosses the interaction gap 33, the cavity 19 is excited and energy is extracted by means, for example, of another induction loop 37.

The klystron, thus far described, is well known in the prior art. According to the invention, however, the various cavities 15, 17 and 19 may be tuned by means of tuning elements 39, 41 and 43 which may be identical to each other.

Referring particularly to FIGURES 2, 3 and 4, a typical tuning element 39, in accordance with the invention, is shown. The envelope of cavity 15 is defined by the cylindrical wall 45 sealed to side plates 47 and 49 which carry drift tubes 21 and 23 projecting inwardly into the cavity to form the interaction gap. A tubing element 39 includes a hollow metal tube 51 sealed at one end in the opening 53 of the cylindrical wall 45, such as by welding, brazing and the like. The other end of the tube 51 is sealed as, for example, by the provision of a sealing cap 55 which is suitably sealed thereto. Both the cavity and the tuning element may be made of materials conventionally used in devices of this kind, such as copper, for example.

In order to tune the cavity 15 in accordance with the present invention, an adjusting tool 57 is inserted through the open end of the tube 51 and rotated as shown by the arrow 59 whereby the tube is moved as indicated by the arrow 61 to either of the positions represented by the numerals 51 or 51". The change of position of the tube or tuner within the cavity varies the reactance of the cavity by changing the configuration of the electromagnetic field within the cavity and, in essence, also changing the distribution of the capacitance and inductance within the cavity to provide a different resonant frequency.

In a klystron such as illustrated, the change in frequency will be more pronounced as the tube is moved closer to the interaction gap since, at this point, the highest electric and electromagnetic fields are present.

After adjustment of the tube 39, the tool is removed and the outside of the cavity presents a smooth surface with no protrusions whereby normal handling of the cavity will not change the position of the tube 51.

Thus, it is seen that a simplified tuner is provided which, although it permits the resonant cavity itself to be sealed to the atmosphere, is itself open to the atmosphere whereby an adjusting tool may be inserted for adjusting its position. The tube 51 is relatively rigid so that it is supported by the wall of the cavity and remains in the position to which it is set by the adjusting tool. To provide additional rigidity,

a it has been found that the tube may be filled with a rigid material, such as an epoxy resin.

Referring to FIGURES and 6, another embodiment of the invention is shown whereby the tuner 139 is disposed in a cavity 115 identical to the cavity with the exception of the tuning element itself. In this instance, the tuner 139 includes a hollow tube 151 for the insertion of the adjusting tool 57. However, the tube 151 includes, in addition thereto, an extension 63 which may be in the form of a cylindrical section. Greater variations in tuning may be accomplished by means of a tuner of the type shown in FIGURES 5 and 6 because the variations of capacity and inductance in the cavity is greater for a given change of position of the larger area tuning element.

The embodiment shown in FIGURE 7 includes a cavity which has a portion 161 within the evacuated envelope and another portion 162 which is external thereto. A cylindrical ceramic member provides the vacuum envelope while leaving the two sections of the caivty electrically connected. The tuner may comprise a hollow tube 163 provided with a cylindrical tuning element 164. In this instance, the hollow tube need not be sealed to form a part of the evacuated envelope.

It can be appreciated that the above-described arrangements are merely illustrations of the principles of the invention. Numerous other arrangements and modifications may be devised by one skilled in the art without departing from the spirit and scope of the invention. One application could be in the movement of an electrode or other element within the vacuum envelope of an electron tube.

I claim:

1. In a klystron tube of the type having interaction gaps surrounded by resonant cavities defined by one or more walls, an elongated hollow member of deformable metal having one end secured to a cavity wall and its other end extending into the cavity in cooperative relationship with the interaction gap in said cavity, said elongated hollow member having no portion which extends outside of said cavity, and means including means defining an opening through said cavity wall communicating with the interior of said hollow member for adjusting from outside the cavity the position within the cavity of said elongated hollow member to thereby permit tuning of the cavity.

2. A tuner for a reentrant resonant cavity, said cavity comprising a wall including reentrant means defining a capacitive gap therein, said tuner comprising a deformable elongated metal member wholly within said cavity and mounted at one end on said wall in spaced relation to said reentrant means and to said gap, said elongated member extending within said cavity into proximity with said gap and having a hollow portion communicating with the exterior of said cavity, whereby to permit insertion of an adjusting tool within the hollow portion of said elongated member to move said member within the cavity to adjust its position relative to said gap.

3. A tuner for a resonant cavity, said cavity having a wall defining a portion of the cavity and said cavity having two coaxial, hollow, reentrant members defining a gap therebetween, said tuner comprising an elongated metal member wholly within said cavity and mounted at one end thereof on said wall in spaced relation to said reentrant members and to said gap, said elongated member having a hollow portion open at said one end and communicating with the exterior of said cavity through a hole in said wall in registry with said opening at said one end, the other end of said elongated member extending within said cavity into proximity with said gap, whereby to permit insertion of an adjusting tool within the elongated member to move said member within the cavity to adjust its position relative to said gap.

4. The method of tuning a resonant cavity enclosing a deformable elongated metal member having a hollow portion communicating with the exterior of said cavity, said method comprising the steps of inserting an adjusting tool into said hollow portion of said elongated member, applying force to the interior of said elongated member to produce deformation thereof and then removing said adjusting tool.

5. The method of claim 4 wherein said cavity is electrically operated during said steps.

References Cited by the Examiner UNITED STATES PATENTS 2,356,414 8/1944 Linder 333-83 2,660,711 11/1953 Garbuny 333-83 X 3,169,206 2/1965 Nelson 3155.53 X

HERMAN KARL SAALBACH, Primary Examiner.

R. D. COHN, Assistant Examiner. 

1. IN A KLYSTRON TUBE OF THE TYPE HAVING INTERACTION GAPS SURROUNDED BY RESONANT CAVITIES DEFINED BY ONE OR MORE WALLS, AN ELONGATED HOLLOW MEMBER OF DEFORMABLE METAL HAVING ONE END SECURED TO A CAVITY WALL AND ITS OTHER END EXTENDING INTO THE CAVITY IN COOPERATIVE RELATIONSHIP WITH THE INTERACTION GAP IN SAID CAVITY, SAID ELONGATED HOLLOW MEMBER HAVING NO PORTION WHICH EXTENDS OUTSIDE OF SAID CAVITY, AND MEANS INCLUDING MEANS DEFINING AN OPENING THROUGH SAID CAVITY WALL COMMUNICATING WITH THE INTERIOR OF SAID HOLLOW MEMBER FOR ADJUSTING FROM OUTSIDE THE CAVITY THE POSITION WITHIN THE CAVITY OF SAID ELONGATED HOLLOW MEMBER TO THEREBY PERMIT TUNING OF THE CAVITY. 